The background of this image shows the mean cerebral
blood flow of all the subjects undergoing the stress tasks (here,
mental arithmetic) acquired using the continuous arterial spin labeling
(CASL) technique. The foreground shows the detected activation in
the right prefrontal cortex -- an area long associated with anxiety
and depression -- when the subjects are under stress.

Image Courtesy: Jiongjiong Wang, PhD, and John A. Detre, MD,
University of Pennsylvania School of Medicine